miRNAs are non-coding RNA molecules that are between 19 and 30 nucleotides in length, which are believed to play a role in regulating approximately 30 per cent of all human genes with their dysregulation implicated in the progression of various diseases such as cancer, heart disease and Parkinson's. Illumina believes its new high-density expression array will help researchers better understand the role miRNAs play in regulating messenger RNA (mRNA) and gene expression. According to the company, currently available assays can be prohibitively expensive for large studies and the launch of its miRNA expression profiling panels at a cost of $95 (€67) per sample allows 'rapid and reproducible miRNA expression profiling at a price less than half that of other commercially available methods'. "We are offering miRNA products at half of the cost of other commercially available methods so that researchers can conduct larger studies at a price they can afford," said Tanya Boyaniwsky, Illumina's marketing manager for Gene Expression. The human miRNA panel contains 735 assays that detect the 470 known human miRNA sequences described in the Sanger Institute's miRBAse database as well as a further 265 potential sequences that have been suggested in the scientific literature. In addition, the mouse miRNA panel features 380 assays for those miRNA discovered in mice. miRNA profiling has distinct advantages over mRNA-based gene expression approaches as a single miRNA can regulate several genes, leading to potentially larger effects on disease progression. There are also less miRNAs to look for than mRNAs (a predicted 1000 compared to over 30,000 mRNAs per cell) making experiment analysis somewhat simpler. In addition, they are less likely to be degraded in the formalin-fixed, paraffin-embedded (FFPE) samples that have been collected from various biopsies and as such are associated with a vast wealth of clinical history. While some options are now coming to market to enable researchers to accurately study these samples, verification using miRNA profiling could lead to a more confident analysis of highly degraded samples. According to Illumina's website, the array matrix-platform has the highest built in feature redundancy of any currently available array to deliver increased reproducibility and improved signal to noise ratios. The system will enter a marketplace already served by Agilent's microarray-based miRNA assay and Applied Biosystems' TaqMan-based real-time PCR miRNA assay. Indeed, recent work using Applied Biosystems TaqMan-based real-time PCR miRNA assay has found that three miRNA molecules form an important part of the p53 tumour suppressor network, suggesting potential new approaches for the treatment of various cancers. However, according to Integrated DNA Technologies (IDT) these technologies can only be used to detect known and proposed miRNA sequences. IDT has launched a miRNA discovery kit miRCAT to enable researchers to discover new miRNA sequences in conjunction with various sequencing techniques. Illumina has acknowledged this fact and will be updating the probes used in the array as more are discovered. "We are committed to regularly updating these products with newly discovered miRNAs as well as information from internal small RNA discovery projects conducted on Illumina's Genome Analyzer," said Boyaniwsky.